So, I was doing a little maintenance on my 87 300TDT today with the rear suspension and I found a piece of steel line over the drivers side suspension components. I would say this would be 3/8 ( or metric equiv.) completely rusted off on both ends. I can't tell what it was coaming from or going to. It is the size of fuel lines but it is not. Both fuel appear to be there. It is not brake of course nor is it going to the hydraulic system. Could it be a vent? Any other ideas?

Although I do not understand your exact reference location, there may be drain tubes for the sun roof at the rear just in front of the bumper and outboard.

Now someone who really knows will jump in.

Buzz

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Buzz
1977 300D 151K (TMU) DB922 Pastel Blue w/Blue
1981 300SD 450K DB753 Astral Silver w/Black
1987 190D Turbo 340K DB199 Black Pearl w/Black
1990 350SDL 190K DB199 Black Pearl w/Black
1994 E320 Convertible 65K DB(9)744 Brilliant Silver w/Grey
1995 E300 Diesel 150K DB (5)904 Midnight Blue w/Saddle

Well I don't think so. They seem to run along side the fuel lines for a bit.

There are three lines attached to the fuel tank, the fuel feed, the fuel return both run all the way to the engine compartment, and the vent line which runs from the tank to almost in front of the driver's side rear wheel where its end points downward. The vent line usually has a valve with a rubber boot on it attached to the line with a short piece of hose and two spring clamps.

It also may be that a failed line has been replaced with a new line and the original failed section was left in place because it can be difficult to remove the damaged line without fooling with the good ones especially in the area above the sub frame.

I thought it may be fuel vent line but wasn't sure. How is it attached to the tank? Is there a rubber fitting?